Atom-economical synthesis of the functionalized spirocyclic oxindole-butenolide via three-component [2 + 2 + 1] cycloaddition strategy

Abstract

The intermolecular [2 + 2 + 1] multicomponent cycloadditions from readily available isocyanides, activated alkynes and isatins are disclosed. This reaction proceeds by way of a Michael addition–nucleophilic addition–intramolecular cyclization sequence, thus providing new access to spirocyclic oxindole-butenolide with exclusive stereoselectivity in an efficient and atom-economical manner. A broad range of isatins and isocyanides including sterically demanding ones are also found to be compatible with the present protocol, which offers an opportunity for the construction of a new compound library. This protocol also allows the insertion of carbon monoxide into organic molecules without the aid of transition metal catalyst after hydrolysis process. Moreover, the cycloaddition–hydrolysis process by step can be further developed into a practical and powerful one-pot strategy in good yields together with convenient experimental set-up, which adds to its attractiveness.